Remove stack.yaml

Seems unneeded

```
trace: haskell-nix.project : both 'stack.yaml' and 'cabal.project' files exist.  Using 'cabal.project'. set 'projectFileName = "stack.yaml";' to override this.'
```

flake.nix

@@ -24,7 +24,6 @@
                   qemu,
                 }:
                 haskell-nix.hix.project {
-                  compiler-nix-name = "ghc966";
                   src = builtins.path {
                     path = ./.;
                     name = "riscv-formal-source";
@@ -37,6 +36,7 @@
                       tools = {
                         cabal = { };
                         hlint = { };
+                        haskell-language-server = { };
                       };
                       nativeBuildInputs = [
                         qemu

shell.nix

@@ -0,0 +1,16 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  riscv64-linux = pkgs.pkgsCross.riscv64.__splicedPackages;
+in
+pkgs.mkShell {
+  nativeBuildInputs = [
+    riscv64-linux.gcc
+    riscv64-linux.binutils
+    riscv64-linux.glibc
+  ];
+
+  shellHook = ''
+    echo "RISC-V Linux cross-compilation environment initialized!"
+  '';
+}